Effects Of Negative Pressure Irrigation On Growth And Water Use Efficiency Of Main Vegetable Crops In South China

Water is the major factor restricting agricultural development.The objective of this paper is to explore the effects of different water conditions on crop growth and development,water use efficiency and quality in order to provide theoretical basis and technical reference for high-yield,water-saving and high-quality production of facility vegetable in south China.In order to select a suitable negative pressure for the growth of pepper(Capsicum annuum L.)and Chinese cabbage(Brassica campestris ssp.chinensis L.)in south of China,a pot experiment was conducted to investigate the effects of different negative pressure levels(-5.0 kPa,-10.0 kPa and-15.0 kPa)on soil moisture,crop yield,crop quality,total water consumption and water use efficiency in2 types of vegetable soils(alluvial garden soil and red-garden soil);A field experiment was conducted to compare the effects of drip irrigation(NPK,separate application of water and fertilizer)and water-fertilizer integrated negative pressure irrigation(NPK,NP,NK,PK)on growth,head quality,water and nutrient use efficiency of cauliflower.The main results were as follows:(1)The effects of different water supply negative pressures on growth and water use efficiency of pepper showed that:Under the negative pressure condition of-5.0kPa,the relative soil water content was 61.6%and 60.5%,the pepper yield was 256.0g/pot and 141.7 g/pot in alluvial and red soil,respectively,which were significantly higher than those under-10.0 kPa and-15.0 kPa treatments.During the growth stage of pepper from May 4 to July 21,the total water consumption in alluvial soil was 21.5dm~3 under-5.0 kPa treatment,higher than that under-15.0 kPa treatment;while the value in red soil was 17.6 dm~3 under-5.0 kPa and was greater than those under both-10.0 kPa and-15.0 kPa.The water use efficiency of pepper under-5.0 kPa treatment was 2.14 kg/m~3 in alluvial soil and 1.69 kg/m~3 in red soil,which were both higher than those under-15 kPa treatment.The water consumption intensity of pepper in alluvial soil was high at the blooming and fruit-setting stage,with a higher value of0.403 dm~3/d under-5.0 kPa than under-15.0 kPa treatment.As for red soil,the water consumption intensity was high at the fruiting stage,also with a higher value of 0.335dm~3/d under-5.0 kPa than under-10.0 kPa and-15.0 kPa treatments.The fruit length,diameter and single weight of pepper in red soil were the optimal under-5.0 kPa treatment,while in alluvial soil they were the best under-10.0 kPa treatment.In terms of pepper yield and water use efficiency,the irrigation level of-5.0 kPa is suitable for pepper in the two selected soils.(2)The effects of different water supply negative pressures on growth and water use efficiency of Chinese cabbage showed that:The biomass and root system activity(TTC reduction)of Chinese cabbage was the highest at-5.0 k Pa treatment in 2 types of vegetable soils.Along with the decrease of water supply pressure,biomass and root system activity decreased significantly.Proline content was the highest at-10.0 kPa treatment,significantly higher than that of-5.0 kPa and-10.0 kPa treatments.Water use efficiency was the lowest under-5.0 kPa treatment,significantly lower than that of-10.0 kPa and-15.0 kPa treatments.By analyzing the biomass,water use efficiency and physiological responses to soil moisture of Chinese cabbage,the suitable negative pressure was-5.0 kPa in 2 kinds of tested soils,and the moisture content was 25%for the soil derived from alluvial garden soil and 19%for soil derived from red-garden soil.(3)The capsicum and Chinese cabbage in alluvial garden soil of yield and soil moisture content were higher than red garden soil under the same negative pressure water supply,the yield increased by 80.7%～165.3%and 125.4%～153.1%respectively,and the soil water content increased by 19.3%～43.6%and 30.2%～43.4%respectively.The water use efficiency of two crops in alluvial garden soil were also higher than red garden soil under-5.0 kPa treatment,increased by 26.6%and 26.8%respectively.(4)The field experiments on cauliflower results showed that:Under the treatments of negative pressure irrigation combined with nitrogen,phosphorus and potassium fertilizer,the economic yield of cauliflower was the highest,18.68 t/hm~2,which increased by about 30%than that of drip irrigation,and the economic coefficient was 32%under that treatment,significantly higher than that of drip irrigation.The content of soluble sugar and VC of Cauliflower was the highest under the treatments of negative pressure irrigation combined with N,P and K fertilizer,which increased by 22%and 13%than that under drip irrigation without fertilizer,but14%and 9%than that under drip irrigation with fertilization.The water consumption of cauliflower during the whole growth stages under negative pressure irrigation was lower than that under drip irrigation,which decreased by 14%～31%.The water use efficiency of cauliflower under negative pressure irrigation was 38 kg/m~3～44 kg/m~3,significantly higher than that under drip irrigation,which increased by 53%～78%than that under drip irrigation.At the same level of nitrogen,phosphorus and potassium application,the utilization efficiency of nitrogen fertilizer under negative pressure irrigation was 31%,similar to that under drip irrigation.The utilization efficiency of phosphorus and potassium fertilizer was 20%and 76%respectively,which increased by 39%and 61%than that under drip irrigation.The results showed that the negative pressurized fertigation not only can promote the growth of cauliflower,ensure the yield,but also can improve the quality of vegetables and make the water and nutrient use efficiency increased greatly.